The present invention relates to a process for producing a meat analogue or substitute by injection molding.
Extensive investigations have been made on production of a meat analogue or substitute by the use of an extruder. Meat analogues produced from plant protein are now on the market and have gained public favor. A conventional process uses a single screw extruder, and it has disadvantages in that the permissible water and oil contents of the product must be inevitably decreased in view of the mechanism of the single screw extruder and, therefore, products are necessarily obtained in a dry condition and need troublesome rehydration before use.
In recent years, the production of a meat analogue by the use of a twin screw extruder has been investigated mainly in European countries. It has been found that with the twin screw extruder, a wide variety of starting materials can be used. Based on these findings, and further with the development of a cooling die, a process for production of a meat analogue by the use of a twin screw extruder is now under extensive investigation in order to overcome the above problems which result from use of a single screw extruder.
In the known process using a twin screw extruder, the die is limited in its shape and cannot be freely designed because the structure of the die exit influences the distribution and fluid characteristics of the starting material used in the extruder. Particularly in production of large-sized products, a problem arises in that when a starting material having a high water and oil content is used, sufficient cooling cannot be performed and the product cannot retain its suitable form followed by atmospheric explosion, because it is necessary to increase the opening of the die for production of large-sized products. For this reason, the die opening must be decreased in size and thus only thin products can be produced in the known process using a twin screw extruder.
The influences of the die form on the phenomena in the extruder can be said to be caused mainly by a flow resistance produced by the flow characteristics of a starting material in the neighborhood of the die. That is, since the resistance value cannot be kept constant due to the die form, a die which can be used for a specified starting material is often unusable for other starting materials. When the flow resistance is too low, even if the screw mechanism of the extruder has a sufficient conveyance ability, a starting material with high temperature and high pressure cannot be held in the top portion of the extruder and thus the starting material flies off as fragile small particles.